Return Fluid Separator

ABSTRACT

A separator for drilling waste including a tank comprising an inlet and an outlet; a screening device disposed within the tank; a conduit coupled to the outlet; and a rotary valve coupled to the conduit. A separator including a tank having an inlet and an outlet; a trough in fluid communication with the tank; and a screening device having a plurality of members disposed within the tank, wherein the screening device is configured to direct an effluent phase through the members into the trough and a solids phase to the outlet. A method of separating drilling waste including flowing a return fluid to an inlet of a tank; and directing the return fluid against a screening device disposed within the tank, wherein an effluent phase of the return fluid passes through the screening device and wherein a solids phase of the return fluid falls to an outlet of the tank.

BACKGROUND OF INVENTION

1. Field of the Invention

Embodiments disclosed here generally relate to a separator for drilling wastes. Specifically, embodiments disclosed herein relate to a separator for receiving a return fluid from a well and separating a solids phase from an effluent phase. More specifically, embodiments disclosed herein relate to separator for separating gumbo from drilling return fluid.

2. Background Art

Oilfield drilling fluid, often called “mud,” serves multiple purposes in the industry. Among its many functions, the drilling mud acts as a lubricant to cool rotary drill bits and facilitate faster cutting rates. Typically, the mud is mixed at the surface and pumped downhole at high pressure to the drill bit through a bore of the drillstring. Once the mud reaches the drill bit, it exits through various nozzles and ports where it lubricates and cools the drill bit. After exiting through the nozzles, the “spent” fluid returns to the surface through an annulus formed between the drillstring and the drilled wellbore.

Furthermore, drilling mud provides a column of hydrostatic pressure, or head, to prevent “blow out” of the well being drilled. This hydrostatic pressure offsets formation pressures thereby preventing fluids from blowing out if pressurized deposits in the formation are breeched. Two factors contributing to the hydrostatic pressure of the drilling mud column are the height (or depth) of the column (i.e., the vertical distance from the surface to the bottom of the wellbore) itself and the density (or its inverse, specific gravity) of the fluid used. Depending on the type and construction of the formation to be drilled, various weighting and lubrication agents are mixed into the drilling mud to obtain the right mixture. Typically, drilling mud weight is reported in “pounds,” short for pounds per gallon. Generally, increasing the amount of weighting agent solute dissolved in the mud base will create a heavier drilling mud. Drilling mud that is too light may not protect the formation from blow outs, and drilling mud that is too heavy may over invade the formation. Therefore, much time and consideration is spent to ensure the mud mixture is optimal. Because the mud evaluation and mixture process is time consuming and expensive, drillers and service companies prefer to reclaim the returned drilling mud and recycle it for continued use.

Another significant purpose of the drilling mud is to carry the cuttings away from the drill bit at the bottom of the borehole to the surface. As a drill bit pulverizes or scrapes the rock formation at the bottom of the borehole, small pieces of solid material are left behind. The drilling fluid exiting the nozzles at the bit acts to stir-up and carry the solid particles of rock and formation to the surface within the annulus between the drillstring and the borehole. Therefore, the fluid exiting the borehole from the annulus is a slurry of formation cuttings in drilling mud. Before the mud can be recycled and re-pumped down through nozzles of the drill bit, the cutting particulates must be removed.

Apparatus in use today to remove cuttings and other solid particulates from drilling fluid are commonly referred to in the industry as “shale shakers.” A shale shaker, also known as a vibratory separator, is a vibrating sieve-like table upon which returning solids laden drilling fluid is deposited and through which clean drilling fluid emerges.

In the North Sea and the United States Gulf Coast, drillers commonly encounter argillaceous sediments in which the predominant clay mineral is sodium montmorillonite (commonly called “gumbo shale” or “gumbo”). Such heavy, high-volume solids are usually encountered when drilling top-hole sections of formation. If not removed, the soft, sticky, swelling clay cuttings, i.e., gumbo, may clog separator screens and/or otherwise adhere to surfaces of the processing equipment, fouling tools and plugging piping. Those of ordinary skill in the art will appreciate that gumbo is typically only encountered in approximately 1% of the entire well; however, removal of the gumbo may prolong the life of the equipment and is often necessary for efficient processing of the returned drilling waste.

Accordingly, there exists a need for more separators that more efficiently process drilling waste or drilling muds.

SUMMARY OF INVENTION

In one aspect, embodiments disclosed herein relate to a separator for drilling waste including a tank having an inlet and an outlet; a screening device disposed within the tank; a conduit coupled to the outlet; and a rotary valve coupled to the conduit.

In another aspect, embodiments disclosed herein relate to a separator for drilling waste including a tank having an inlet and an outlet; a trough in fluid communication with the tank; and a screening device having a plurality of members disposed within the tank, wherein the screening device is configured to direct an effluent phase through the plurality of members into the trough and a solids phase to the outlet.

In another aspect, embodiments disclosed herein relate to a method of separating drilling waste including flowing a return fluid from a well to an inlet of a tank; and directing the return fluid against a screening device disposed within the tank, wherein an effluent phase of the return fluid passes through the screening device and wherein a solids phase of the return fluid falls to an outlet of the tank.

Other aspects and advantages of the invention will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a separator in accordance with embodiments disclosed herein.

FIG. 2 is a perspective view of a rotary valve in accordance with embodiments disclosed herein.

DETAILED DESCRIPTION

In one aspect, embodiments disclosed herein relate to a separator for drilling wastes. Specifically, embodiments disclosed herein relate to a separator for receiving a return fluid from a well and separating a solids phase from an effluent phase. More specifically, embodiments disclosed herein relate to separators for separating gumbo from drilling return fluid.

Referring to FIG. 1, a separator 100 is shown. Separator 100 includes a tank 102 having an inlet 104 and an outlet 106. The inlet 104 is configured to receive a fluid for separating a fluids phase and a solids phase. In one embodiment, inlet 104 receives a return fluid from a well. More specifically, in certain embodiments, inlet 104 receives a return fluid comprising gumbo.

Separator 100 further includes a screening device 106 disposed within tank 102. Screening device 106 may include a plurality of members disposed within the tank, wherein the screening device 106 is configured to separate a solids phase from an effluent phase of a return fluid. The plurality of members of the screening device 106 may include axially aligned longitudinal members 108, as shown in FIG. 1. The plurality of axially aligned longitudinal members 108 may be evenly spaced or may be spaced at varying distances. In one embodiment, the plurality of members of the screening device 106 may be tubulars. For example, screening device 106 may include a plurality of 2 inch diameter tubulars spaced approximately 2 inches apart. In other embodiments, the plurality of members may be solid bars.

In an alternate embodiment, the screening device 106 may include a plurality of members, wherein the members are axially aligned horizontal members (not shown). In yet other embodiments, the screening device 106 may include a plurality of axially aligned longitudinal members and axially aligned horizontal members, thereby forming a mesh of members. One of ordinary skill in the art will appreciate that the spacing between the plurality of members of the screening device 106 may be selected based on the size of the desired solids phase to be separated from the return fluid.

The plurality of members of the screening device 106 may be individually installed and aligned within the tank 102. Alternatively, screening device 106 may include an assembled screen which includes the plurality of members. In this embodiment, the screen may be placed inside the tank 102 and secured in place by any mechanism known in the art. For example, tank 102 may include a track (not shown) in which the screen of the screening device 106 slides into. Additionally, the screen may be mechanically fastened, e.g., by bolting, screwing, riveting, etc., welding the screen into place, or any combination thereof.

As shown, the screening device 106 extends across a length L of the tank 102, such that fluid entering the separator 100 may not bypass the screening device 106 around ends of the screening device 106. Additionally, the screening device 106 extends across a width w of the tank 102, such that fluid entering the separator 100 may not bypass the screening device 106 around sides of the screening device 106. Accordingly, gumbo or solids larger than the spacing between the plurality of members of the screening device 106 are prevented from flowing up and out of, i.e., bypassing, the separator 100. The screening device 106 may be disposed within tank 102 at a predetermined angle a with respect to a wall of the tank 102. The predetermined angle a may vary based on the size and shape of the tank 102, the specific configuration of the screening device 106 (e.g., the number and spacing of the plurality of members), and the solids phase to be separated from the return fluid (e.g., the size and expected quantity of gumbo to be filtered). For example, screening device 106 may be disposed at an angle a between about 10 and about 80 degrees from the side of the tank. In other embodiments, the screening device 106 may be disposed at an angle a of between about 20 and about 45 degrees from the side of the tank.

Specifically, screening device 106 may be disposed within tank 102 such that a first end 110 is positioned higher than a second end 112 within the tank 102. As used herein, first end 110 and second end 112 may refer to all ends of the plurality of aligned members of the screening device 106, an end of a screen having a plurality of aligned members, or both. For example, the first end 110 of the screening device 106 may be disposed proximate a first upper edge 114 of the tank 102 and the second end 112 may be disposed proximate an opposite lower end 116 of the tank 102.

As shown, the inlet 104 of the tank 102 is located below the first end 110, i.e., the upper end, of the screening device 106. Thus, as fluid enters the tank 102 through inlet 104, the fluid is directed against the screening device 106. An effluent phase of the fluid passes through the screening device 106 and a solids phase sized larger than the spacing between the plurality of members of the screening device 106 is trapped or separated from the effluent phase and falls to the bottom of the tank 102. As shown in FIG. 1, tank 102 may include a non-flat bottom surface 118 to assist in guiding the separated solids phase toward the outlet 106 of the tank 102. For example, the bottom surface 118 of the tank 102 may be conical or angled toward the outlet 106.

The effluent phase of return fluid that passes through the screening device may then be transferred from the tank 102 to a separate container, distribution vessel, or secondary separators (not shown). A trough 120 or other conduit may be coupled to the tank 102 along a side of the screening device 106 opposite the inlet 104. The trough 120 is configured to transfer the effluent phase to the separate container, distribution vessel, or secondary separators.

A conduit 122 is coupled to the outlet 106 of the tank 102 and configured to transfer the separated solids phase from the separator 100 to other process equipment, for example, a secondary separator 126, storage container, or an overboard line. An isolation valve 124 may be coupled to the conduit 122 to close the conduit 122, thereby stopping flow of the solids phase through the conduit 122. The flow of solids phase may be stopped to allow, for example, maintenance to be performed on one or more components of the process equipment, e.g., secondary separator 126, downstream of the conduit 122. Although the isolation valve 124 is shown disposed proximate the center of the conduit 122, one of ordinary skill in the art will appreciate that the isolation valve 124 may be disposed anywhere along the length of the conduit 122. For example, in one embodiment, the isolation valve 124 may be disposed proximate the outlet 106 or between the outlet 106 and a first end 129 of the conduit 122. The isolation valve may be any type of valve known in the art, for example a knife gate valve.

A rotary valve 128 is coupled to a second end 130 of the conduit 122. One example of a rotary valve 128 is a DM500 Airlock, commercially available from Mac Equipment, Kansas City, Mo. As shown in FIG. 2, the rotary valve 128 includes a material inlet 132 into a housing 134. A rotor 136 extends into a chamber 135 of the housing 134. A plurality of vanes 138 are coupled to the rotor 136 and extend therefrom into the chamber 135. The rotor 136 is coupled to a motor (not shown) that rotates the rotor 136 and, therefore, the vanes 138 inside the chamber 135. Accordingly, the separated solids phase 144 of the return fluid flows from the conduit 122 (FIG. 1) to the material inlet 132 of the rotary valve 128 and into a partitioned segment of the chamber 135 disposed between the vanes 138 of the rotary valve 128. As the motor turns the rotor 136 and vanes 138, the solids phase 144 is rotated or moved, as indicated by arrow R, through the housing 134 of the rotary valve 128 from the material inlet 132 to a material outlet 140 of the rotary valve 128.

The rotary valve 128 may be operated at varying speeds based on, for example, the consistency of the solids phase, the size of the rotary valve, and the flow rate of the solids phase. In one embodiment, the rotary valve 128 may be operated at 19 revolutions per minute. The rotary valve 128 may also include various features that allow the valve 128 to process gumbo material. For example, in certain embodiments, the rotary valve 128 may be modified to include a radiused pocket rotor, thereby smoothing out the portion where the blades are welded to the shaft, a Nedox coating to improve the resistance to abrasive particles in the gumbo, and air jets along the discharge to aide in removing material that might otherwise stick to the discharge. The Nedox coating is a chrome compound that may be sprayed onto the rotor 136 and vanes 138 and includes a Teflon compound infused into the pores to provide an abrasion resistant, slick surface to assist in transferring the solids phase (e.g., gumbo) through the rotary valve 128 from the separator 100 (FIG. 1). One of ordinary skill in the art will appreciate that other coatings may be applied to the rotor 136 and vanes 138 to reduce adhesion of the solids phase to the rotary valve 128. Arrows 142 in FIG. 2 show introduction of air into the chamber 135 of the rotary valve 128 to assist in removing material from the rotary valve 128. Rotary valve 128 may thus be used to facilitate the transference of gumbo from separator 100 (FIG. 1) to secondary process equipment, such as secondary separator 126 (FIG. 1).

Referring back to FIG. 1, while solids phase is separated from a primarily effluent phase of the drilling waste, the solids phase may be directed to a secondary separator 126. In one embodiment, secondary separators 126 may include separators for high-volume solids, such as the Mongoose® Shaker, commercially available from M-I Swaco, L.L.C., in Houston, Tex. The effluent phase may pass through separator 100 through trough 120 to a flow distribution vessel (not shown). The flow distribution vessel (not shown) may be used to divert the flow of effluent phase between various separators (not shown).

A method of separating drilling waste is now disclosed with reference to FIG. 1. A return fluid from a well is flowed to inlet 104 of tank 106. The return fluid may include drilling muds and drilling waste, including gumbo. Due to the position of the screening device 106 in the tank 102, the return fluid is directed against the screening device 106. As the return fluid hits the screening device 106, an effluent phase of the return fluid passes through the screening device, thereby filtering out or separating the solids phase of the return fluid, which, as mentioned above, may include gumbo. The effluent flows through the trough 120 coupled to the tank 102 for further processing or storage. In one embodiment, the effluent may be transferred by the trough 120 to a flow distribution vessel (not shown), which directs the effluent to one or more separators. These separators may include multiple deck separators, such as the MD-3 Shale Shaker, commercially available from M-I Swaco, L.L.C., in Houston, Tex.

Due to the position or alignment of the screening device 106 in the tank 102, as described above, the solids phase separated by the screening device 106 falls to the bottom surface 108 of the tank 102. The curvature or angling of the bottom surface 108 of the tank 102 helps direct the solids phase of the return fluid to the outlet 106 of the tank 122. The solids phase is transferred to the rotary valve 128 which is operated to transfer the solids phase to secondary process equipment. For example, rotary valve 128 may be operated to transfer the solids phase to a secondary separator 126, which may further filter or dry the solids phase. In one embodiment, a distribution box 146 may be disposed downstream of the rotary valve 128 and configured to separate the solids phase between one of a plurality of secondary separators 126 a, 126 b, 126 c. Those of ordinary skill in the art will appreciate that depending on the type of secondary separation required, the type and/or number of secondary separators 126 may vary.

The isolation valve 124 may be actuated to close the valve 124 to prevent solids phase from flowing to the rotary valve 128. The isolation valve 124 may be closed to allow maintenance or cleaning work on the secondary process equipment, e.g., secondary separator 126.

Advantageously, embodiments disclosed herein provide for a separator for receiving a return fluid from a well and separating a solids phase from an effluent phase that reduces or prevents splash-over or bypassing of the screening device. Furthermore, embodiments disclosed herein may provide a separator for efficiently separating gumbo from a drilling return fluid. Advantageously, embodiments disclosed herein provide a separator that allows gumbo to settle down in a tank rather than flowing over a shaker. Additionally, embodiments disclosed herein provide a separator having a rotary valve configured to gradually feed gumbo from a receiving tank to a shaker, overboard, or other processing equipment.

While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims. 

What is claimed:
 1. A separator for drilling waste comprising: a tank comprising an inlet and an outlet; a screening device disposed within the tank; a conduit coupled to the outlet; and a rotary valve coupled to the conduit.
 2. The separator of claim 1, further comprising a trough coupled to the tank configured to remove an effluent phase of the drilling waste.
 3. The separator of claim 1, further comprising an isolation valve coupled to the conduit.
 4. The separator of claim 3, wherein the isolation valve is disposed between the outlet and the rotary valve.
 5. The separator of claim 1, wherein the inlet is disposed on a side of the tank.
 6. The separator of claim 1, wherein the screening device is disposed in the tank at a predetermined angle.
 7. The primary separator of claim 6, wherein the screening device extends from a first upper edge of the tank to an opposite lower end of the tank.
 8. The primary separator of claim 6, wherein the inlet is disposed below an upper edge of the screening device.
 9. The primary separator of claim 1, wherein the screening device comprises a plurality of axially aligned longitudinal members.
 10. The primary separator of claim 1, wherein the rotary valve comprises a rotor and a coating applied to the rotor.
 11. The primary separator of claim 1, wherein the rotary valve comprises air jets disposed proximate a discharge end of the rotary valve.
 12. A separator for drilling waste comprising: a tank comprising an inlet and an outlet; a trough in fluid communication with the tank; and a screening device comprising a plurality of members disposed within the tank, wherein the screening device is configured to direct an effluent phase through the plurality of members into the trough and a solids phase to the outlet.
 13. The separator of claim 12, further comprising a conduit coupled to the outlet.
 14. The separator of claim 12, further comprising a rotary valve coupled to the conduit.
 15. The separator of claim 12, further comprising an isolation valve coupled to the conduit.
 16. A method of separating drilling waste comprising: flowing a return fluid from a well to an inlet of a tank; and directing the return fluid against a screening device disposed within the tank, wherein an effluent phase of the return fluid passes through the screening device and wherein a solids phase of the return fluid falls to an outlet of the tank.
 17. The method of claim 16, further comprising moving the solids phase from the outlet through a conduit to a rotary valve.
 18. The method of claim 17, further comprising actuating the rotary valve to transfer at least a portion of the solids phase to a secondary separator.
 19. The method of claim 16, further comprising flowing the effluent through a trough coupled to the tank to a flow distribution vessel.
 20. The method of claim 16, further comprising actuating an isolation valve. 